| 摘要 |
A flyback generator for a television receiver, in a sweep system driving the vertical-deflection yoke of a cathode-ray tube, comprises a storage capacitor with a low-voltage side grounded through a charging transistor and a high-voltage side connected through an isolating diode to the live terminal of a d-c supply. The charging transistor conducts during scanning but is cut off during flyback by the operation of a first switching transistor while a second switching transistor connects the low-voltage side of the charged storage capacitor to the live supply terminal whereby its high-voltage side is carried to a voltage Vf equaling twice the supply voltage Vs, less any voltage drop across the charging transistor. This high-voltage side is connected to the yoke through an output stage of a power amplifier saturated during flyback. The coupling between the first switching transistor and the charging transistor comprises a voltage-regulating network including a Zener diode connected across the supply; when the supply voltage Vs rises above a threshold Vt established by the Zener diode, a branch current mirroring the Zener current reduces the conductivity of the charging transistor to generate during scanning a voltage Vs =2(Vs-Vt) thereacross which results in a partial discharge of the storage capacitor; thus, the maximum VF of the flyback voltage Vf, occurring upon switchover, is twice the threshold voltage Vt.
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